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Major outbreak of equine herpesvirus [EHV] among sport horses in Eastern France

French authorities and the FEI [Federation Equestre Internationale/International Federation for Equestrian Sports] are urging vigilance following a major outbreak of equine herpesvirus [EHV] among sport horses in Eastern France.

At least 22 properties are reported to have been affected by the outbreak since January [2018], with an estimated 200 horses sick.

The French monitoring agency RESPE [Reseau d'epidemio-surveillance de la filiere equine, Equine epidemiology and pathology surveillance network] said while many events had been cancelled, many others had gone ahead with heightened security measures.

The RESPE triggered its crisis team on [26 Apr 2018] as part of efforts to ensure the outbreak is ultimately contained.

The regions of Normandy, Brittany, and Loire Valley are most affected.

While the outbreak has affected mainly sport horses, breeding stock has also been involved. At least one training centre has been affected.

The RESPE, in an update today [5 May 2018], said no new cases had been confirmed in recent days, although tests were being carried out on some horses that are possibly infected.

While most cases have been in the west of France, they have also been reported in Ile-de-France in the east and in the Gironde.

"This represents about 200 sick or suspicious horses," RESPE said. "Unfortunately, all the cases are not reported to the RESPE and, with the information gathered, there is an under-declaration of cases actually present in the field."

It says sport horses, Thoroughbreds, and trotters have so far been affected.

The symptoms observed are mostly fever, depression, and nasal discharge.

Several series of abortions have also been recorded and 6 cases of the neurological form of the disease have been reported, resulting in 4 horses being euthanized.

Clinical signs of disease are reduced among vaccinated hoses, it said. However, some vaccinated horses have also exhibited classic respiratory forms of the disease, abortions and neurological forms.

Its spread appeared to be related to gatherings and the introduction/return of horses without adequate biosecurity measures.

"At this stage, epidemiological links around equestrian events are suspected between several stables housing sport horses, mainly with respiratory or asymptomatic forms. No link has yet been confirmed for the moment."

In the coming weeks, many gatherings will be held in the affected regions, some involving many horses. Some of these horses will have participated in events in "risk areas" the previous weeks.

The RESPE urged owners whose horses took part in recent events where horses suspected or confirmed with EHV were found to have taken part to suspend their participation in further events for the time being. Those with horses in affected areas should carefully monitor the health of their animals, it said.

"The typing and characterization of viral strains is under way in the various outbreaks to allow us to understand the peculiarities of this epizootic," it said. "The 1st results point to the circulation of several different viral strains."

It said vaccination remained an effective preventive measure.

The RESPE said horse owners and event organisers had to play their part in limiting the spread of the disease. It issued its standard protocols for sport horse events, saying non-compliance would allow the virus to continue to spread, "causing a paralysis of activities".

The situation seemed to be stabilising, it said today, with no new cases confirmed since [27 Apr 2018]. However, tests results on several sick horses were awaited.

Many rallies were canceled over the weekend from [28 Apr to 1 May 2018]. Others, it said, were held with reinforced control measures, mostly appreciated by the participants. No post-competition cases have been reported yet.

"It should be noted that the competitions held have also had between 20 and 30 percent cancellation of participation. For the coming weeks, many organizers are wondering about whether or not to hold their gatherings."

The agency said that while the situation appeared to be stabilising, recommendations remained unchanged regarding equestrian gatherings:

The suspension or postponement of gatherings in sites that have recently hosted suspicious or confirmed horses.

Owners should not participate in rallies if their horses have competed in events with confirmed outbreaks or with sick horses pending confirmation. This measure also applies if suspected cases are present in their stabling centre.

In vaccinated horses, the clinical signs are mostly reduced or absent, but vaccinated horses can, if infected, also spread the virus.

The main route of transmission is directly by air from infected horses coughing or snorting. The virus can survive in the environment for a couple of weeks. Indirect transmission can also occur, for example via unwashed hands, tack or clothing etc.

Aborted foetuses are highly contagious.

Once the horse has been infected it becomes a silent carrier of the virus for the rest of its life. The virus remains in a latent state (without any clinical signs) but can be activated by stress and cause disease at any time.

Incubation time may be as short as 24 hours, but typically is 4-6 days or sometimes longer.

Diagnosis
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In acute cases of respiratory or neurological disease, nasal swab sampling can be undertaken. The sample is analysed by a test kit that can detect the virus.

The FEI said prevention measures on competition sites were applicable to all:
- check and record the body temperature of the horse twice daily. Any temperature over 38.5 [deg C/101.3 deg F] should immediately be reported to the veterinary delegate/veterinary service manager;
- assess your horse's general condition: appetite, drinking, behaviour, breathing rate, heart rate, urination and defecation, eye or nose discharges, how the horse is standing and moving, swollen legs;
- have dedicated tack/equipment for each horse and disinfect the bit after riding;
- do not share buckets; no common water trough;
- wash and disinfect hands;
- do not let horses sniff each other, limit contact as much as possible, including human contact, apart from rider and regular groom.

Advice for FEI organising committees
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If local horses are kept at the event site you should assess the EHV status of these horses. Ask a veterinarian to sample 10-20 percent of these horses about 10 days before the event.

Clean and disinfect the stables and other facilities where FEI horses will be. This is standard practice for FEI stables and must always be carried out.

Examination on arrival must always be carried out before horses are allowed to enter the FEI stables. It is advised that the temperatures of the arriving horses are recorded.

Under the current conditions it is critical that the FEI Veterinarian is given the requested resources in terms of space, possibility to wash and disinfect hands, personnel and resources to run the isolation stable.

The FEI supports the RESPE's advice to request a veterinary certificate of every horse arriving at the venue that is issued within 48 hours of departure from the stable of origin. The certificate should state the following:
- identity of the horse;
- identity, contact information, and signature of the issuing veterinarian;
- date and place of issue;
- statement that the horse has been located at a stable where there has been no signs of EHV infection for the last 14 days.

Control the density of horses in the warm-up arena. Too many horses on a limited area increases the risk for transmission of the disease.